Method of making a flat foundation for a floor without substantial excavation and foundation made by said method

ABSTRACT

Cellular foil ( 3 ) is unfolded between the surface of earth base course ( 1 ) and the first floor layer ( 5 ) during building the subsoil, which cellular foil ( 3 ) is poured over with fill ( 4 ) from loose material at least up to filling the compartments. A bedding ( 2 ) from loose material, optimally from sand, is created under the cellular foil ( 3 ). Geotextile ( 6 ) may be incorporated to the area under the cellular foil ( 3 ). Bedding ( 2 ) of lower grain size than that of the fill ( 4 ) is preferably used, wherein the fill ( 4 ) has optimal grain size of 8 to 63 mm. Compaction is done by at least eight travels of roller of 10 to 11 tons weight, also including vibrations when the height of fills is exceeding 25 cm above the cellular foil ( 3 ).

TECHNICAL FIELD

The technical solution relates to a new method of shallow foundation offloor, particularly for high load bearing floors of buildings such aslarge-area halls etc. New arrangement of floor subsoil is created usingthis method.

BACKGROUND ART

During foundation of industry floors, such system of making-up ofsubsoil and construction layers of earth plate should be selected, toensure maximum fulfilment of the floor reliability criteria. Usedmethods of floor foundation include shallow foundation and deepfoundation.

Currently known method of shallow foundation of floor includes creationof classical distributing gravel pad from psephite material such ascrushed quarry aggregate, crushed ballast, gravel, gravel sand, andsand. Using this method, surface of earth base course is removed first,often in high volumes, and subsequently made-up grounds of loosematerials are performed. Gravel pad created in this way is sometimesreinforced with the help of geotextile or chemical solidification.Subsoil created using these methods consists of pad of loose material,possibly intercalated with geotextile, and of the first floor layerplaced on the pad. In case of using the method of chemicalsolidification, for instance lime stabilisation, chemically solidifiedlayer is additionally contained as an underlayer located on the earthbase course. For instance in the case of lime stabilisation, beforemade-up of gravel pad, solidified layer is created first by the processwhen the earth layer is mixed with lime, which, after binding water fromterrain, will create solidified layer on the basis of calcium carbonate.The first floor layer is then placed directly on this chemicallysolidified layer or on gravel pad placed on the chemically solidifiedlayer. Disadvantage of these methods include risk of non-uniformload-bearing capacity and uneven settlement of the whole redevelopedarea and associated possible problems during cracking of the flooringassembly in the future. Consequences are manifested as local kneeling orheaving of the floor and cracking of the floor. Other disadvantages ofthe aforementioned methods include the need to remove material inconsiderable volumes, necessity to ensure landfills for muckedmaterials, transportation costs associated with supply of fillingmaterials, and time demands. Other disadvantage when using chemicalsolidification is the risk of environmentally unfavourable action ofchemical preparations, namely lime.

Known method of deep foundation is the method of consolidation with thehelp of pillars, usually filled with gravel. Using this method includesboring pits of various lengths and diameters into the earth base course,which are subsequently filled with gravel of various grading or withlime. Pillars created in this way are sometimes combined with gravel pador geotextile. The first floor layer is then placed on the backgroundcreated in this way. In this case, the subsoil consists of earth basecourse, pillars of various lengths and widths, optional gravel padand/or possibly one or several layers of geotextile, and the first floorlayer. Other known methods of deep foundation are the methods ofsolidification with the help of injection, such as Soil-mixing orcompaction grouting. In such case, the subsoil consists at least ofearth base course, a layer chemically solidified by injection, and thefirst floor layer. Disadvantages of existing methods of deep foundationare, beside its high demands on mechanization, time and financing, alsoand particularly the uncertainty of ensuring uniform load-bearingcapacity of the floor and even settlement of the floor across the wholeredeveloped area. The consequences are usually, just like in the case ofaforementioned methods of floor shallow foundation, cracking of floorsin buildings and local sinking or heaving of the floor.

So called cellular foil is known for consolidation of sole of terrainswithout buildings, such as roads, walkways, pavements, slopes, grassplots, playgrounds etc. Its arrangement is known for instance frompatent specifications of U.S. Pat. No. 5,449,543, WO 97/16604 and of CZPV 1286-98. This cellular foil is created from strips on the basis ofplastics that are vertically positioned and interconnected by weldingseams or other joints so that a web structure with vertical walls iscreated, which in a state stretched on a plane contains system ofvertically open compartments.

DISCLOSURE OF INVENTION

The above mentioned disadvantages are eliminated to a considerableextent by the invention. Method of floor shallow foundation is solved,by which the floor subsoil for buildings, halls in particular, is builton modified earth base course, where the floor is shallow founded sothat the first floor layer from concrete-based material is laid onmodified background. The essence of the invention is that at least onelayer of cellular foil in unfolded state is laid down onto thebackground before laying down the first floor layer, than this cellularfoil is overfilled with fill from loose material reaching at least up tothe foil height, thus filling the cavities in chambers of the cellularfoil, the fill is then compacted and the first floor layer is laid downonly now on this compacted fill.

Before laying down the cellular foil, the earth base course ispreferably equipped with at least one pad from loose material on thebasis of gravel and/or sand, which is then compacted, and thus beddingfor cellular foil is created.

Generally, material of finer grading than fill is preferably used asbedding. Sand is the best material for bedding.

During building of floor subsoil, some layer built before placing of thefirst floor layer can be equipped with geotextile stretched in plane.Exceptionally, the geotextile can be placed in multiple layers.

Quarry stone having sharp edges and grading from dust particle size upto 63 mm, optimally of the grain size 8 to 63 mm, is preferably used asthe fill.

The fill mentioned above is compacted, preferably by at least eighttravels of roller with mass of 10 to 11 metric tons.

In the case when the fill is created to the height of at least 25 cmabove the cellular foil, vibration of travelling roller can bepreferably switched on.

New structural arrangement of the floor subsoil is created by theproposed invention. Floor subsoil made by the process according to theinvention differs from the existing solutions particularly in that itcontains a pad from cellular foil with compartments and from fillbetween the surface of earth base course and the first floor layer onthe basis of concrete. Cellular foil is in a state unfolded to a planeand the fill consists of loose material such as gravel, sand and/orgravel sand filling compartments of this cellular foil and reaches atleast from the lower edge of the cellular foil to at least upper edge ofthe cellular foil.

At least one layer of bedding of grain size finer than the grain size ofthe fill is located under the cellular foil and above the surface of theearth base course, preferably considering properties of terrain.

Floor subsoil according to the invention can contain at least onegeotextile unfolded in a planar way, preferentially between the firstfloor layer and the surface of the earth base course. Generally, it ispreferential, when the geotextile is located under the cellular foil,i.e. directly under the foil or in some layer under the cellular foil oron some layer located under the cellular foil.

The invention allows creation of subsoil with uniform load-bearingcapacity and equal settlement of the subsoil. The subsoil andconsequently also the floor are solid, are not sinking locally norspinning in a plane, edges are not lifting, the floor is not crackingand the whole surface of the floor has the same load-bearing capacity.The invention is utilizable particularly for industrial floors, factorybuildings and halls with high load bearing floor such as freezingplants, supermarkets, garages etc. It can replace the existing methodsof floor foundation, both methods of shallow foundation and methods ofdeep foundation as well. It can be also combined with the methodsmentioned above, as the case may be. It can eliminate the necessity tobuild pillars and/or remove large volumes of earth base course. Thesubsoil can be created quickly and without demanding modifications orsubstantial interference with background from earth base course.

REVIEW OF FIGURES ON DRAWINGS

The invention is illustrated using drawings, where

FIG. 1 shows representative subsoil according to the example 1,consisting of earth base course, bedding, cellular foil, fill and lowerfloor layer,

FIG. 2 shows process of placing layers one to another according to theinvention during making subsoil illustrated on the previous figure,

FIG. 3 shows representative subsoil according to the example 2,consisting of earth base course, geotextile, bedding, cellular foil,fill and lower floor layer,

FIG. 4 shows process of placing layers one to another according to theinvention during making subsoil illustrated on the previous figure,

FIG. 5 shows spatial arrangement of subsoil according to the example 2,

FIG. 6 shows spatial arrangement of subsoil according to the example 1,

FIGS. 7 to 9 show other variants of subsoil made by the procedureaccording to the invention.

EXAMPLES OF EMBODIMENT OF INVENTION Example 1

Example of embodiment of the invention is the procedure of making thesubsoil according to FIG. 2 and the subsoil for freezing store accordingto FIGS. 1 and 6 made by the procedure.

Drainage bedding 2 of broken quarry gravel aggregate with particle sizeof 32 to 63 mm has been brought to the surface of earth base course 1evened to horizontal level. Bedding 2 has been levelled and compacted by10 travels of roller weighing 10 metric tons with vibration. Compactedbedding 2 reached the height of 25 cm. Twenty cm high cellular foil 3has been placed on the surface of this background and stretched in aplane so that it covers all the area designed for the building. Then,the fill 4 from quarry gravel aggregate with grain size of 32 to 63 mmhas been gradually brought to the cellular foil 3. The aforesaid fill 4has been dumped and a spread over the cellular foil 3 until it filledits compartments and reached the height of approx. 10 cm over the topedge of the cellular foil 3. The fill has been compacted with 12 travelsof roller. Then, dumping of next 10 cm of fill 4 continued, this timefrom quarry gravel aggregate with grain size of 0 to 63 mm; Then, whenthe fill 4 reached 20 cm over the cellular foil, its compaction has beenperformed by twenty travels of roller weighing 10 metric tons, afterwhich next 10 cm of the same material has been brought and compacted bytwelve travels of the same roller using vibrations. Then, the overallheight of the fill 4 reached 50 cm, and the cellular foil 3 has beenincorporated in its lower part. The first floor layer 5 in the form ofsteel-fibre-reinforced concrete has been laid down onto such treatedbackground. The floor, not shown on drawings, has been made on thissubsoil, where next layers has been made in a common way, laying downheat insulation and reinforced concrete with tubular heating. Thesubsoil has been used for foundation of floor in a freezing plant.

The subsoil made by the aforesaid process contained, listed from thebottom to the top, earth base course 1, 25 cm high bedding 2, a pad onit from fill 4 and cellular foil 3, where the fill 4 was 50 cm high intotal, and the aforesaid 20 cm high cellular foil 3 has beenincorporated in its lower part, and the first floor layer 5 has beencontained on this pad. Static load tests proved that the values ofdeformation modulus considerably exceeded stated requirements. Thesubsoil has been evaluated as a homogenous one with minimal differencesin quality within the framework of the building. Values of the subsoilquality requirements has been considerably exceeded.

Example 2

Other, in the inventor's opinion the optimal example of embodiment ofthe invention is the process of making the subsoil according to the FIG.4 and the subsoil for metal works hall according to FIGS. 3 and 5 madeby the procedure.

Geotextile 6 of approximately 2 mm height has been placed on the surfaceof earth base course 1 evened to horizontal level by mucking the arablelayer and plow pan. Drainage bedding 2 from sand with particle size of0.63 to 2 mm has been brought on it. Bedding 2 has been levelled andcompacted by 10 travels of roller weighing 11 metric tons. Compactedbedding 2 reached to the height of 10 cm. Fifteen cm high cellular foil3 has been placed on the surface of this background and stretched in aplane so that it covers all the area designed for the building. Then,the fill 4 from quarry gravel aggregate with grain size of 8 to 63 mmhas been gradually brought to the cellular foil 3. The aforesaid fill 4has been dumped and a spread over the cellular foil 3 until it filledits compartments and reached the height of approx. 10 cm over the topplane of the cellular foil 3. The fill has been compacted with 12travels of roller weighing 11 metric tons. Then, dumping and a spreadingof the fill 4 continued. Later, when the fill 4 reached approximately 20cm over the cellular foil 3, its compaction has been performed by eighttravels of roller weighing 11 metric tons, after which next 10 cm of thesame material has been brought. Then the surface has been compacted byten travels of the same roller using vibrations. After compaction, theoverall height of the fill 4 reached 45 cm, and the cellular foil 3 hasbeen incorporated in its lower part. The first floor layer 5 in the formof concrete has been laid down onto background treated in this way. Inthis way, subsoil has been created on which the floor, not shown ondrawings, has been made, where next layers has been made in a commonway, laying down concrete, heat insulation and tile flooring, and abuilding of metal works has been raised.

This subsoil contained, listed from the bottom to the top, earth basecourse 1, approximately 2 mm high geotextile 6, 10 cm high bedding 2, apad on it from cellular foil 3 and fill 4, where the fill 4 was 45 cmhigh in total, and the aforesaid 15 cm high cellular foil 3 has beenincorporated in its lower part, and the first floor layer 5 has beensituated on this pad.

Uniform load-bearing capacity of the floor and uniform settlement of thefloor has been achieved.

Example 3

Embodiment of the invention has numerous variants, consistent inpossible omitting of bedding 2 and omitting of geotextile 6, orincorporation of geotextile 6 in arbitrary height during creation ofsubsoil. The most frequent examples of these alternatives in theframework of the invention are illustrated on FIGS. 7 to 9.

FIG. 7 shows the subsoil created on earth base course 1, and containingonly pad from cellular foil 3 and fill 4, and the first floor layer 5placed on it.

FIG. FIG. 8 shows the subsoil created on earth base course 1, andcontaining geotextile 6, next the pad from cellular foil 3 and fill 4,and the first floor layer 5 placed on it.

FIG. 9 shows the subsoil created on earth base course 1, and containingbedding 2 on which resides geotextile 6, next the pad from cellular foil3 and fill 4, and the first floor layer 5 placed on it. Theabovementioned examples of embodiment only demonstrate options ofembodiment of the invention, without limiting them, geotextile 6 can befor instance incorporated as intermediate layer inside the bedding 2 orthe fill 4.

1. A method of making a flat foundation for a floor of a structurewithout substantial excavation comprising the steps of: excavating anearth base course (1), providing at least one drainage bedding layer (2)on the earth base course (1), compacting the bedding layer (2) usingmultiple travels of a roller on the bedding layer, spreading at leastone layer of a plastic cellular foil (3) having vertically extending andupwardly open compartments on the drainage bedding layer (2),overfilling the compartments of said cellular foil (3) with fill (4) ofQuarry stone of grain size 8 to 63 mm so that the fill (4) extends abovethe height of the cellular foil (3) by at least 25 cm, compacting thefill (4) over the cellular foil by at least eight travels of a roller of10 to 11 metric tons weight and with vibration to form compacted fill(4), and laying a floor layer (5) of the structure on the compactedfill.
 2. A method of making a flat foundation for a floor according toclaim 1 wherein the material of the drainage bedding layer (2) is finerthan the material of the fill (4).
 3. A method of making a flatfoundation for a floor according to claim 1, including the further stepof providing at least one layer of geotextile (6) below the cellularfoil (3).
 4. A method of making a flat foundation for a floor accordingto claim 1 in which at least one further layer of fill (4) is placedover the compacted fill (4) and wherein the further layer of fill (4) isthen compacted.
 5. A method of making a flat foundation for a flooraccording to claim 1 in which two further layers of fill (4) are placedover the compacted fill (4) and wherein the two further layers of fill(4) are compacted.